This invention relates to a tool for inserting and extracting tire beads into and from their retention seats of respective wheel rims while fully respecting the integrity of said beads whatever the nominal diameter of said wheel rims.
Modern tire removal machines, typically for automobile and other light vehicle wheels and for motorcycle wheels, are known to comprise, inter alia, a usually horizontal self-centering unit provided for locking the wheel rims, and an overlying tool for mounting and removing the respective tires, this acting between the bead retention edge of the wheel rim and the tire bead.
This tool can be adjusted both vertically and horizontally, in order to adapt its operating position to wheel rims of different widths and diameters.
In particular, this tool is supported by a vertical bar slidable in height and supported by a horizontal arm which is slidingly mounted on the top of a column situated behind the self-centering unit.
More specifically, the tool consists of an elongate profiled one-piece body to be positioned transversely to the bar, and comprising two active portions positioned on one and the other side of the bar.
One of the active portions is formed in practice as a blade or tongue intended to lie virtually coplanar with the upper bead retention edge of the wheel rim locked on the self-centering unit, the other presenting a substantially hemispherical head intended to lie facing the bead retention edge and presenting a jutting protuberance situated on the opposite side to that occupied by the blade or tongue.
The purpose of the protuberance is to provide the support and turning region for the usual bead lifting levers used by tire operators in disengaging the beads from the bead retention seats on the respective wheel rims.
As stated, these known tools are in the form of a one-piece body, which has proved unsatisfactory for the following reasons.
In this respect, as modern vehicle and motorcycle wheel rims can have considerably different nominal diameters, the one-piece tool construction means that the tongue or the protuberance on known tools often assumes an operating position relative to the wheel rim which is displaced from the optimum required for easy and correct extraction and insertion of the respective tire beads.
With particular reference to the extraction of a bead from the respective edge of its wheel rim, the optimum position of the tool relative to the wheel rim is that in which the support protuberance for the bead lifting lever is practically parallel to the straight line tangential to that region of the bead retention edge which is close to the protuberance, the blade passing beyond the bead retention edge by a distance of the same order of magnitude as the radial dimension of the bead.
Known tools can occupy an operating position close to the aforedefined optimum for only a part of the range of possible nominal wheel rim diameters, for example medium-large and large diameters, whereas their operating position deviates from the optimum even by a large extent for other diameters within the range, for example intermediate and small diameters.
In particular, if the tool is not correctly positioned relative to a circle of relatively small diameter, the respective protuberance is inclined outwards from the straight line tangential to that region of the bead retention edge behind the protuberance, and the blade extends beyond the end of the bead retention edge by a distance which is relatively large compared with that for wheel rims of intermediate and relatively large nominal diameters.
This inclination of the protuberance results in a corresponding distancing of the respective support region for the bead lifting lever away from the bead retention edge of the wheel rim, thus creating a problem when the bead has to be lifted onto the hemispherical head of the tool to arrange it for extraction.
In this respect, seeing that the inclination of the protuberance increases the distance of its free end from the bead retention edge, and that in order to lift the bead onto the head by the bead lifting lever the bead has to pass beyond the free end of the protuberance, the bead must be deformed to a greater extent than would occur if the protuberance were correctly positioned as aforestated.
In addition to requiring considerable force by the tire operator, this can subject the bead to problems and/or excessive stress, with possible damage such as stretching, local weakening and cracking.
Other possible local damage can also derive from the settling of the bead lifting lever, in particular from the oscillation to which the lever is subjected when, starting from its transverse orientation defined by the wedging of its end between the bead and the respective bead retention edge, it is pulled with force against the protuberance, which as stated is inclined to the tangent passing through that portion of the bead retention edge situated at the protuberance.
These problems assume particular importance for tubeless tires.
Moreover, at the moment the upper bead is extracted from the respective bead retention edge of a wheel rim of relatively small diameter, where as stated the blade extends beyond the end of said bead retention edge by a relatively large distance, the free edge of the blade can interfere with the sidewall of the tire, with consequent inconvenient rubbing between the two during rotation of the self-centering unit.
Consequently, with the self-centering unit in movement similar rubbing also occurs between the sidewall of the tire and the blade during insertion of the lower bead, and between the sidewall and the free end of the protuberance during extraction of the lower bead.
In an attempt to overcome this problem, certain parties, including the Applicant, have proposed tools, again consisting of a one-piece body shaped as specified in the introduction, which are intended to be positioned at the end of a vertical bar such that their angular position can be adjusted.
In particular, these tools comprise an intermediate tube to be mounted as an exact fit on a lower cylindrical end shank of said bar, and be locked thereat by suitable means, such as a ring nut or the like.
In addition, the shank is provided with a surface flattening, and with two transverse adjacent through screws the points of which make contact with said surface flattening.
To swivel the tool in one direction or the other, one of said screws has firstly to be loosened and then the other screwed tightly down.
However this solution has also proved unsatisfactory at least for the following two reasons.
The first is the fact that the loosening and tightening operations are relatively lengthy and complicated.
The second is the fact that as the tool is in one piece, its two opposing active portions cannot be independently adjusted, with the result that when one of them is positioned correctly, the other can occupy an inconvenient position.
Essentially, if the protuberance is positioned virtually parallel to the tangent passing through that part of the circle close to the protuberance, the blade can project excessively from the end of the bead retention edge, and if the blade is positioned to pass beyond the end by a distance of the same order of magnitude as the radial dimension of the bead, the protuberance can be inconveniently inclined to the tangent, with the aforegoing drawbacks.
In this specific sector there is therefore a widely felt need for a tool which is able to overcome the aforesaid problem, without having to use two or more tire removal machines each having a tool suitable for a specific part of the range of current nominal wheel rim diameters.
The main object of the present invention is precisely to satisfy said requirement within the context of a simple, rational, economical, reliable and durable construction.
This object is attained by the characteristics indicated in the claims.
In a general sense, this object is attained by providing a tool in the form of a system of variable shape, which can be adjusted as required on the basis of the nominal diameter of the wheel rim which at that moment is locked on the self-centering unit of a tire removal machine.
In particular, as will be more apparent hereinafter, it comprises two parts, of which one carries the blade and the other supports the head with its protuberance, these being provided with two coaxial annular elements or hubs which are mounted on the cylindrical end shank of the tool holder bar, and are stably coupled together such that their mutual orientation can be adjusted.
At least one of the parts can be torsionally locked to the shank, with the desired orientation.
By means of the aforesaid solution all the objects of the invention are attained, as will be apparent hereinafter.